X-ray computed tomography (CT) is a method which includes: rotating a subject relative to an X-ray source to take transmission images of the subject at different angles; and performing calculation called reconstruction using the obtained transmission images, thereby obtaining a sectional image of the subject. X-ray CT is an essential technique for medical diagnosis, since it is possible to observe inside a subject non-destructively and three-dimensionally by using high penetration of X-ray.
Spatial resolution of X-ray CT mainly depends on spatial resolution of an image detector which obtains a transmission image, and a distance (working distance (WD)) between a subject and the detector. Since there are mechanical limitations, it is generally difficult to extremely shorten the WD. Therefore, it is necessary to improve resolution of the detector in order to improve the spatial resolution.